1. Field of the Invention
The present invention relates to a method of manufacturing slide fastener coupling elements successively from a metal strip by coining and blanking.
2. Prior Art
A variety of methods have been known to produce so-called double-acting or two-way coupling elements for side fasteners. U.S. Pat. No. 2,622,295, issued Dec. 23, 1952 discloses one form of such double-acting coupling elements, which are manufactured by roll-coining a wire stock in a manner as described in U.S. Pat. No. 2,201,068, issued May 14, 1940. The rolling method is disadvantageous in that the rolled wire stock must be reversed in its direction of feed when severed and attached to the beaded edge of a stringer tape, resulting in an increased expenditure of time and labor.
U.S. Pat. No. 3,136,046, issued June 9, 1964 shows a metal strip having longitudinal medial raised portions which are deformed by a punch press into longitudinally spaced coupling projections. With this arrangement, the projections thus produced are of a relatively low profile owing to their height being virtually dependent on the height of the medial lands, and hence the metal strip must be considerably thick for the projections to have a required projection height.